According to the prior art, a carrier member (e.g. a flatcar) of a compound trolley conveyor (not shown) is adapted to travel by being pulled with a drive chain through a trolley. The trolley and the drive chain are connected together by a connection means (not shown) which is capable of making engagement and disengagement.
To start the movement of the carrier member when it is at rest, it is necessary that the carrier member be connected to the drive chain which is traveling, using the connection means. Conversely, for stopping the movement of the carrier member when it is traveling, it is necessary to disconnect the carrier member from the drive chain, using the connection means. In the first case, however, since the drive chain which is traveling is suddenly connected to the carrier member which is at rest, the tractive force is sometimes exerted as an excessive impact force on the carrier member.
Therefore, with a view to buffering such impact force, for example the shock absorber (not shown) disclosed in Japanese Utility Model Laid Open No. 30773/1989 (Application No. 125635/1987) is disposed between a foremost trolley and a front trolley in a compound trolley conveyor. The shock absorber is composed of two piston-cylinder mechanisms disposed concentrically face to face with each other and springs which are compressed by the pistons, whereby an impact force is absorbed by compression of the air in each cylinder and compression of the springs.
In such conventional shock absorber, however, since the buffered energy is accumulated in the compressed air and springs and acts as a repulsive force on the pistons, the pistons repeat pulsations reciprocating in the traveling direction and thereafter stop. Consequently, the carrier member vibrates repeatedly in the traveling direction and this repeated vibration may cause damage to the article on the carrier member.
According to the present invention, in order to solve the above-mentioned problem, there is provided a shock absorber in a compound trolley conveyor, including two cylinders disposed between a foremost trolley and a front trolley of the compound trolley conveyor and connected together face to face with each other and two pistons inserted into the cylinders respectively and interconnected, wherein with movement of the pistons, the air in one of the cylinders is compressed and the air in the other cylinder is exhausted.
According to the shock absorber of the present invention, when an impact force is applied to the carrier member at the time of connection or disconnection between the trolley connected to the carrier member and a drive chain, one piston moves in a direction to compress the air in the associated cylinder, while the other piston moves in a direction to withdraw or exhaust air from the associated cylinder. By such air compressing and withdrawing actions, the impact energy is absorbed to buffer the impact force.
The compressed air in one cylinder slowly flows out to the exterior from the piston-cylinder gap, while the outside air slowly flows into the other cylinder through the piston-cylinder gap. Therefore, there is no fear of the impact energy acting as a repulsive force on the piston and hence the impact force is buffered without pulsation of the carrier member.
An embodiment of the present invention will be described below with reference to the drawings.